This invention relates generally to providing error resilience and concealment for video data.
Video communication is becoming a popular form of communication over the Internet, wireless telephones, and other video telephones. The primary challenge for video communications is the enormous bandwidth required for transmitting video signals. As such, developers have turned to video compression and have proposed a variety of standards for compressing video signals before transmission. One such standard is the Moving Picture Experts Group (MPEG-2) standard, which is described in ISO/IEC 13818-1 (MPEG-2 Systems), ISO/IEC 13818-2 (MPEG-2 Video), dated in 1994 and provided by the International Organization For Standardization (ISO) and the International Electrotechnical Commission (IEC).
One inherent problem with video communications systems is that information may be altered or lost during transmission due to channel noise, for example. As such, error recovery methods are becoming increasingly popular because of the growing interest of transmitting video over unreliable channels, such as wireless networks and the Internet.
Currently, MPEG standards define three types of frames, namely intraframe (I-type) frames, which use no temporal prediction, interframe (P-type) frames, which are predictively encoded based on past I- or P-type frames, and bi-directionally predicted (B-type) frames, which are predictively encoded based on past or future I- or P-type frames. The error resilience and concealment techniques so far have focused primarily on P-type frames, because B-type frames are generally not used for low bitrate MPEG-4 and H.263 compression. Error resilience and concealment techniques, however, may sometimes be complex and computationally taxing. Complex error resilience techniques, for example, may require more bandwidth allocation for error resilience. Additionally, complex error resilience or concealment techniques may require high-speed, and oft expensive, hardware resources. As such, efficient methods of providing error resilience and error concealment that take advantage of cases where B-type frames are used in addition to P-type frames may be desirable.
Efficient techniques may also be desirable in modifying the error resilience of an encoded video bitstream. For example, a device receiving an encoded video bitstream may need to retransmit, or, alternatively, store the encoded video bitstream. In the process of storing or re-transmitting the encoded video bitstream, the device, such as a cell phone or a personal digital assistance (PDA), may perform undesirable complex computations, which may not only consume additional energy but may also be operationally inefficient.
Thus, there is a need to provide an efficient method of error resilience before transmission, retransmission, or storage, and an efficient method of error concealment while receiving an encoded video bitstream.